The field of the invention is in the art of flow measuring devices.
Fluid flow velocity measuring apparatus is well known. The pitot tube is an example that has been in use for two centuries. More recent velocimetry devices are the hot-wire anemometer, and devices using lasers in both doppler shift and non-doppler modes of operation. Other recent developments in airspeed sensors are disclosed in U.S. Pat. No. 3,680,375 by patentees Joy et al; U.S. Pat. No. 3,519,351 by patentee Lerwill; U.S. Pat. No. 3,833,299 by patentee Lang; and U.S. Pat. No. 3,820,896 to patentee Stavis.